During the past few decades, innovative Australian growers have invented novel designs, and made critical improvements to harvest weed seed control machines such as impact mills and chaff carts.
Craig Bignell and his wife Sara Robinson run a 9500ha mixed farming operation on several blocks within a 50km radius of their home farm at Broomehill, in southern WA and use two modes of harvest weed seed control to maximise feed value for their sheep and minimise the impact of burning chaff.
With high weed seed contamination in their grain in the 2000s, the Bignells decided to introduce harvest weed seed control to their weed management program.
In 2008, they purchased two chaff carts, one for each header.
The early model chaff carts were blower systems that experienced some weed seed losses, so when they replaced their headers, the Bignells purchased conveyor-type carts.
Along with being another weed management tool, the chaff carts also provided a valuable fodder source for the Bignell’s sheep flock.
Having keenly watched the development of the Harrington Seed Destructor impact mill, Mr Bignell invested in a hydraulic-drive iHSD impact mill in 2015. Unfortunately, the early models experienced several setbacks, and the Bignells ended up with a collection of spare parts in their shed.
Mr Bignell and his father Dan took these parts and followed a hunch that resulted in the prototype of the mechanicaldrive vertical iHSD that is now on the market.
Their prototype had many problems, but they ran it for 400 hours in the 2017 season.
Soon after, the manufacturers adopted the idea and developed the vertical iHSD that runs off the chopper drive and down to the mill, eliminating the hydraulic system that had caused problems on the original iHSD.
These days, Mr Bignell has a vertical iHSD on one header and a chaff cart on the other.
The Bignells only run the chaff cart in their legume crops, avoiding the fire risk that burning cereal chaff heaps poses. This also reduces the wear-and-tear on the impact mills
that can occur when harvesting legumes. The legumes produce less crop residue, reducing the need to burn while providing high-value feed for their livestock.
The feed value for livestock grazing chaff heaps is about 25–30 per cent higher than that of paddocks harvested with the iHSD and paddocks without any HWSC tool on the header.
For these reasons, the Bignells were keen to keep using the chaff cart system in their operation.
With both systems, it is essential to harvest low and ensure good separation of chaff and straw in the header set-up. This maximises the quantity of weed seed that enters the header and keeps the weed seed in the chaff stream to be processed through the mills or collected in the chaff cart.
Mr Bignell considers crop competition one of the most important tactics for controlling annual ryegrass.
“Crop competition is foundational for weed control as trials repeatedly show that ryegrass seed production doubles in poorly competitive crops,” he says.
“We use competitive cultivars, high seeding rates, eastwest sowing, narrow row spacing and early sowing – all to maximise early crop vigour and quickly close the canopy.”
For more information about integrated weed management, visit the WeedSmart website: www.weedsmart.org.au
